Wood preservatives

ABSTRACT

A method for preserving wood by contacting wood with a composition comprising a polyurethane polymer, non-aqueous solvents, and a wood preservative.

The present invention relates to a method for treating wood to impart protection from wood-decaying organisms.

There are many methods and compositions for preserving wood prior to the time the wood is put in use. Also, preservatives for treating wood in place are available on the market including both oil-based and water-based products. The oil-based products generally consist of petroleum oils with pentachlorophenol or creosote. U.S. Pat. No. 7,959,723 describes one such composition employing oil-soluble preservatives for wood. From the standpoint of toxicity and environmental pollution, these active ingredients are less than desirable.

The problem addressed by this invention is the need for a more environmentally friendly wood treatment composition which is capable of efficaciously imparting active ingredients.

The present invention is directed to a method for preserving wood; said method comprising contacting wood with a wood treatment composition comprising a polyurethane polymer synthesized from i) a polyol, and ii) an isocyanate; at least one organic solvent; and at least one wood preservative selected from among halogenated isothiazolinone biocides, halogenated carbamate fungicides and azole fungicides; wherein the polyol comprises from 1 to 5% poly-i-butylene oxide +99 to 95% p-propylene oxide.

The present invention is further directed to a wood treatment composition comprising a polyurethane polymer synthesized from i) a polyol, and ii) an isocyanate; at least one organic solvent; and at least one wood preservative selected from among halogenated isothiazolinone biocides, halogenated carbamate fungicides and azole fungicides; wherein the polyol comprises from 1 to 5% poly-1-butylene oxide +99 to 95% p-propylene oxide.

All percentages and part per million (ppm) values are on the basis of total weight of the composition, unless otherwise indicated. The terms “a” or “an” refer both to the singular case and the case where more than one exists. All range endpoints are inclusive and combinable. As contained herein all molecular weights are number average molecular weight and are determined by Gel Permeation Chromatography (GPC). It is envisioned that one skilled in the art could select and/or combine multiple suitable and/or preferred embodiments in the present invention.

Polyurethane polymers, as used herein, typically are synthesized from a reaction of isocyanates with polyols, but may contain other functional groups derived from reaction of isocyanates with other monomers, e.g., amide groups derived from carboxylic acids, and ureas derived from amines, e.g. ethylene diamine (EDA) or other polymers, such as polyesters, e.g., polyesters derived from adipic acid and 1,6-hexanediol, 1,4-butanediol and/or neopentyl glycol, or polycarbonates, e.g. polycarbonates derived from poly 1,6-hexanediol carbonate. Suitable isocyanates include, e.g., methylene bis(4-cyclohexylisocyanate) (MCI), methylene bis(4-phenylisocyanate) (MDI), polymethylenepolyphenol isocyanate (pMDI), hexamethylene diisocyanate (HDI), isophorone diisocyanate (IPDI) and toluene diisocyanate (TDI) and combinations thereof. Preferably, the isocyanates of the present invention are IPDI, pMDI, MDI and combinations thereof. More preferably, the isocyanate is IPDI. The polyol used to make the polyurethane comprises p-butylene oxide and p-propylene oxide. Suitably, the polyol used to make the polyurethane comprises at least 1% p-butylene oxide. Suitably, the polyol is 1 to 5% p-butylene oxide +99 to 95% p-propylene oxide. Suitably the isocyanate to polyol molar ratio of the polyurethane polymers is from less than 4 to greater than or equal to 0.1, alternatively from less than or equal to 2 to greater than or equal to 0.1.

Polyurethane polymers of the present invention may be capped or uncapped. If the polyurethane polymers are capped, an amine or alcohol is suitable as a capping agent. Preferably, the capping agent is a monoamine or monoalcohol. Specifically, the capping agent is at least one of a mono primary alkyl amine, mono secondary alkyl amine or mono alcohol with an alkyl group. In accordance with the present invention, a primary amine having a carbon chain length of ≥C₆, a mono alcohol, and a secondary amine are suitable capping agents, and mixtures thereof.

The polyurethane polymer is synthesized in a non-aqueous solvent or a mixture of non-aqueous solvents. Preferably, the amount of solvent is from 60% to 90%, more preferably from 70% to 90%, and most preferably from 75% to 90%. Suitable solvents include ester and ether solvents having a boiling point of at least 150° C., and preferably a flash point of at least 60° C. Examples of such solvents include, alkanes, branched alkanes, aromatics, e.g., Mineral spirits, toluene, benzyl alcohol, xylenes, and alkyl benzenes. A suitable mixture of non-aqueous solvents useful in the present invention is Aromatic 200 (CAS No. 64742-94-5).

The wood treatment composition of the present invention, in addition to polyurethane polymer, further comprises a wood preservative. The wood preservative may be selected from the class of halogenated isothiazolinone biocides, halogenated carbamate fungicides, metal salts of naphthenic acids, and azole fungicides. When the wood preservative is a halogenated isothiazolinone biocide, it preferably comprises a 3-isothiazolone having a C₄-C₁₂ N-alkyl substituent, more preferably a chlorinated 3-isothiazolone, and most preferably 4,5-dichloro-2-n-octyl-4-isothiazolin-3-one (“DCOIT”). Mixtures of wood preservatives may be used. When the polyurethane polymer is combined with DCOIT a suitable composition includes 23% polyurethane polymer solids, 23% DCOIT, and 54% Aromatic 200.

The composition used to treat wood preferably contains from 100 ppm to 40,000 ppm wood preservative, more preferably from 200 ppm to 30,000 ppm, and most preferably from 300 ppm to 25,000 ppm. Preferably, the polymer solids content of the composition is from 10% to 40%, more preferably from 10% to 30%, and most preferably from 15% to 30%. Preferably, the polymer solids to biocide ratio is from 2:1 to 1:2, more preferably from 2:1 to 1:1.

Another critical element of the wood preservation composition is an organic solvent. The polyurethane polymer is diluted with organic solvent. Suitably, the organic solvent is diesel, however other organic solvents known to those of skill in the art may be used. In some embodiments the organic solvent is not the same compound as the non-aqueous solvent of the present invention. As used herein, diesel is defined as the fractional distillation of crude oil between 200° C. (392° F.) and 350° C. (662° F.) at atmospheric pressure, resulting in a mixture of carbon chains that typically contain between 8 and 21 carbon atoms per molecule or biodiesel that is obtained from vegetable oil or animal fats (biolipids) which have been transesterified with methanol (fatty-acid methyl ester (FAME)) and mixtures thereof.

The compositions used in the present invention may optionally contain additional components including but not limited to stabilizers, dyes, water repellents, other wood biocides, fungicides and insecticides, antioxidants, metal chelators, radical scavengers, etc. Stabilizers include, e.g., organic and inorganic UV stabilizers, such as, copper oxide or other copper salts or complexes that resist leaching; zinc oxide; iron salts, iron oxide, iron complexes, transparent iron oxide and nanoparticle iron oxide; titanium dioxide; benzophenone and substituted benzophenones; cinnamic acid and its esters and amides; substituted triazines, such as triphenyl triazine and substituted phenyl triazine UV absorbers, benzotriazole and substituted benzotriazole UV absorbers; hindered amine light stabilizers, used individually or in combination. Water repellents include, e.g., various wax-type water repellents, e.g., paraffin, carnauba, and polyethylene waxes; and silicones. Other wood biocides, fungicides, such as copper metal, bethoxazin and cyproconazole, chlorothalonil, tebuconazole, propiconazole, pentachlorophenol, creosote, copper napthenate, dialkyl dimethyl quaternary ammonium carbonate/bicarbonate, and insecticides include, e.g., those listed in U.S. Pat. No. 6,610,282, e.g., imidacloprid, thiacloprid, permethrin, and etofenprox. Antioxidants include any commercially available antioxidant compounds, e.g., phosphite antioxidants such as IRGAFOS; lactone antioxidants; phenolic antioxidants such as BHT; ascorbic acid; and IRGANOX and the like. Metal chelators include, e.g., EDTA, NTA, 1,10-phenanthroline, ACUMER 3100, DEQUEST, TAMOL 731, tripolyphosphate and other inorganic and organic compounds and polymers useful in chelating or dispersing metal salts. Radical scavengers include, e.g., TEMPO.

Treatment of wood is performed by contacting the wood with the wood treatment composition described herein, preferably under conditions that comply with AWPA Standards T1-16 and meet conditions for use specified in U1-16. In order to provide long term protection, the preservative needs to “fix” in the wood and not deplete too rapidly by volatilization or by leaching when the wood gets wet. It might be expected that enhanced penetration or enhanced movement of the preservative deep into the wood during treatment might also lead to reduced fixation of the organic wood preservative. However, it was discovered that the polymers used to provide enhanced penetration also effectively fix the organic biocide in the wood as seen by the dislodgeable residue assay in the examples.

EXAMPLES Synthesis of Polyurethane Polymers:

The Following Polyurethanes were synthesized from a bis hydroxy terminated polypropylene oxide (95-99%)/polybutylene oxide (1-5 wt %) mixture and a diisocyanate. 150 mL of anhydrous bis hydroxy terminated polypropylene oxide (95-99%)/polybutylene oxide (1-5 wt %) mixture in aromatic 200 (solvent, 10-30 wt % solution), diisocyanate (2 molar equivalents of isocyanates to hydroxyl groups), was charged with 0.003% of a Tin catalyst (dibutyltin dilaurate) to the reactor. The reactor was heated to 90° C. with overhead stirring. The reaction mixture was held at 90° C. for 1 h.

In the examples where the polyurethane is capped, the residual isocyanate is measured using Surface SWYPE™ test strips. The reaction product was cooled to room temperature and the capping reagent, mono amine (1 equivalent amine to unreacted isocyanate) was added to cap the remaining isocyanate groups in the reaction mixture. Alternatively, when mono alcohol (1 equivalent hydroxyl to unreacted isocyanate) was used as the capping reagent it was added at 90° C. and reacted for an additional 1 h at 90° C. The reaction is continued at 90 C till no free isocyanate was observed when tested with SWYPE test strips. The polymer solids of the PU solution was estimated from the conversion and the amount of reactants used for the reaction. The polymer solids are calculated as the sum of the reactive components in the synthesis of the polymer.

Procedure to Determine Diesel Compatibility:

In a clear, 1 oz vial, 0.1 gram of the polymer (on a 100% polymer solids basis) is diluted with 9.9 grams of diesel fuel (weight/weight) to a 1% solution of the polymer. The sample is maintained at room temperature for 48 hours. After 48 hours, the solution is checked for incompatibility, defined as phase separation, precipitation of the polymer as solids, and/or turbidity.

Calculations of Hansen Solubility Parameters:

Hansen solubility parameters (HSP) for the various polyurethane end cap segments were computed using HSPiP software (Purchased from https://www.hansen-solubility.com/). Predicted HSPs (using the Y-MB method), namely, the HSP for the dispersion (D), polar (P), and hydrogen bonding (H) contributions (all SP in MPa1/2), the total SP (calculated using the predicted HSP), and “End cap distance from diesel” were computed. According to the HSP theory, the distance between two materials is a measure of the solubility. The smaller the distance the more soluble the fluids are within one another. HSP data for a “diesel” was obtained from the literature (Batista et al. J. Am. Oil Chem. Soc. V92, 95, 2015).

δ_(T)=√{square root over (δ_(D) ²+δ_(P) ²+δ_(H) ²)}

R _(a)=√{square root over (4(δ_(D1)−δ_(D2))²+4(δ_(P1)−δ_(P2))²+4(δ_(H1)−δ_(H2))²)}

δ_(D1)=Dispersive solubility parameter for diesel=14.51 δ_(D2)=Dispersive solubility parameter for a given end group (δ_(D)) δ_(P1)=Polar solubility parameter for diesel=3.18 δ_(P2)=Polar solubility parameter for a given end group (δ_(P)) δ_(H1)=H-bonding=Dispersive solubility parameter for diesel=5.97 δ_(H2)=H-bonding solubility parameter for a given end group (δ_(H))

TABLE 1 Diesel Compatibility of Polyurethane made with 95% p-iPO + 5 wt % piBO and IPDI with various cap segments (MW = 2000 to 4000) Diesel compatibility Calculated Hansen Solubility Parameters (1 wt. %) (MPa^(1/2)) for End Cap Segment and “End p-iPO Mn = 2000 p-iPO Mn = 4000 Example End Capping Cap” distance from “Diesel” (Ra) EX-1-12; EX-1-12; # Reagent Polyol (bis OH) δ_(T) δ_(D) δ_(P) δ_(H) Ra Comp 1-5 Comp 1-5 EX-1  Methanol 5 w% p-iBO + 28.4 19.1 16 13.6 17.5 YES YES 95 wt % p-iPO EX-2  1-Butanol 5 wt % p-iBO + 22.7 17.5 10.4 10 10.2 YES YES 95 wt % p-iPO EX-3  1-Pentanol 5 wt % p-iBO + 21.9 17.4 9.5 9.2 9.2 YES YES 95 wt % p-iPO EX-4  1-octanol 5 wt % p-iBO + 19.8 16.9 7.6 6.9 6.6 YES YES 95 wt % p-iPO EX-5  Docosanol 5 wt % p-iBO + 17.1 16.2 4.3 3.4 4.4 YES YES 95 wt % p-iPO EX-6  Dimethylamine 5 wt % p-iBO + 26.1 18.3 14.3 11.9 14.7 YES YES 95 wt % p-iPO EX-7  Dihexylamine 5 wt % p-iBO + 19.7 16.7 8.1 6.6 6.6 YES YES 95 wt % p-iPO EX-8  Didecylamine 5 wt % p-iBO + 18.3 16.4 6.3 5 5 YES YES 95 wt % p-iPO Ex-9  1-hexylamine 5 wt % p-iBO + 22.7 17.5 10.9 9.6 10.4 YES YES 95 wt % p-iPO Ex-10 1-Octylamine 5 wt % p-iBO + 21.9 17.4 9.9 8.8 9.3 YES YES 95 wt % p-iPO EX-11 1-dodecylamine 5 wt % p-iBO + 20 17 8.1 6.8 7 YES YES 95 wt % p-iPO Ex-12 1-Octadecylamine 5 wt % p-iBO + 18.6 16.6 6.5 5.2 5.4 YES YES 95 wt % p-iPO Comp. 1 1-butylamine 5 wt % p-iBO + 25.6 18.1 13.2 12.4 13.9 NO NO 95 wt % p-iPO Comp. 2 1-pentylamine 5 wt % p-iBO + 24.5 17.9 12.2 11.5 12.6 NO NO 95 wt % p-iPO Comp. 3 1-hexylamine 100 wt % p-iPO 22.7 17.5 10.9 9.6 10.4 NO NO Comp. 4 1-Octylamine 100 wt % p-iPO 21.9 17.4 9.9 8.8 9.3 NO NO Comp. 5 1-dodecylamine 100 wt % p-iPO 20 17 8.1 6.8 7 NO NO

TABLE 2 Diesel Compatibility of Polyurethane made with 99% p-iPO + 1 wt % piBO and IPDI with various cap segments (MW = 2000 to 4000) Diesel compatibility Calculated Hansen Solubility Parameters (1 wt. %) (MPa^(1/2)) for End Cap Segment and “End p-iPO Mn = 2000 p-iPO Mn = 4000 Example End Capping Cap” distance from “Diesel” (Ra) EX-13-24; EX-13-24; # Reagent Polyol (bis OH) δ_(T) δ_(D) δ_(P) δ_(H) Ra Comp 6-7 Comp 6-7 EX-13 Methanol 1 wt % p-iBO + 28.4 19.1 16 13.6 17.5 YES YES 99 wt % p-iPO EX-14 1-Butanol 1 wt % p-iBO + 22.7 17.5 10.4 10 10.2 YES YES 99 wt % p-iPO EX-15 1-Pexitanol 1 wt % p-iBO + 21.9 1.7.4 9.5 9.2 9.2 YES YES 99 wt % p-iPO EX-16 1-octanol 1 wt % p-iBO + 19.8 16.9 7.6 6.9 6.6 YES YES 99 wt % p-iPO EX-17 Docosanol 1 wt % p-iBO + 17.1 16.2 4.3 3.4 4.4 YES YES 99 wt % p-iPO EX-18 Dimethylamine 1 wt % p-iBO + 26.1 18.3 14.3 11.9 14.7 YES YES 99 wt % p-iPO EX-19 Dihexylamine 1 wt % p-iBO + 19.7 16.7 8.1 6.6 6.6 YES YES 99 wt % p-iPO EX-20 Didecylamine 1 wt % p-iBO + 18.3 16.4 6.3 5 5 YES YES 99 wt % p-iPO Ex-21 1-hexylamine 1 wt % p-iBO + 22.7 17.5 10.9 9.6 10.4 YES YES 99 wt % p-iPO Ex-22 1-Octylamine 1 wt % p-iBO + 21.9 17.4 9.9 8.8 9.3 YES YES 99 wt % p-iPO EX-23 1-dodecylamine 1 wt % p-iBO + 20 17 8.1 6.8 7 YES YES 99 wt % p-iPO Ex-24 1-Octadecylamine 1 wt % p-iBO + 18.6 16.6 6.5 5.2 5.4 YES YES 99 wt % p-iPO Comp.6 1-butylamine 1 wt % p-iBO + 25.6 18.1 13.2 12.4 13.9 NO NO 99 wt % p-iPO Comp.7 1-pentylamine 1 wt % p-iBO + 24.5 17.9 12.2 11.5 12.6 NO NO 99 wt % p-iPO

TABLE 3 Diesel Compatibility of Polyurethane made with 95% p-iPO + 5 wt % piBO and MDI with various cap segments (MW = 2000 to 4000) Diesel compatibility Calculated Hansen Solubility Parameters (1 wt. %) (MPa^(1/2)) for End Cap Segment and “End p-iPO Mn = 2000 p-iPO Mn = 4000 Example End Capping Cap” distance from “Diesel” (Ra) EX-25-30; EX-25-30; # Reagent Polyol (bis OH) δ_(T) δ_(D) δ_(P) δ_(H) Ra Comp 8 Comp 8 EX-25 Methanol 5 wt % p-iBO + 28.4 19.1 16 13.6 17.5 YES YES 95 wt % p-iPO EX-26 Docosanol 5 wt % p-iBO + 17.1 16.2 4.3 3.4 4.4 YES YES 95 wt % p-iPO EX-27 Dimethylamine 5 wt % p-iBO + 26.1 18.3 14.3 11.9 14.7 YES YES 95 wt % p-iPO EX-28 Didecylamine 5 wt % p-iBO + 18.3 16.4 6.3 5 5 YES YES 95 wt % p-iPO Ex-29 1-hexylamine 5 wt % p-iBO + 22.7 17.5 10.9 9.6 10.4 YES YES 95 wt % p-iPO Ex-30 1-Octadecylamine 5 wt % p-iBO + 18.6 16.6 6.5 5.2 5.4 YES YES 95 wt % p-iPO Comp. 8 1-pentylamine 5 wt % p-iBO + 24.5 17.9 12.2 11.5 12.6 NO NO 95 wt % p-iPO

TABLE 4 Diesel Compatibility of Polyurethane made with 99% p-iPO + 1 wt % piBO and MDI with various cap segments (MW = 2000 to 4000) Diesel compatibility Calculated Hansen Solubility Parameters (1 wt. %) (MPa^(1/2)) for End Cap Segment and “End p-iPO Mn = 2000 p-iPO Mn = 4000 Example End Capping Cap” distance from “Diesel” (Ra) EX-31-36; EX-31-36; # Reagent Polyol (bis OH) δ_(T) δ_(D) δ_(P) δ_(H) Ra Comp 9 Comp 9 EX-31 Methanol 1 wt % p-iBO + 28.4 19.1 16 13.6 17.5 YES YES 99 wt % p-iPO EX-32 Docosanol l wt % p-iBO + 17.1 16.2 4.3 3.4 4.4 YES YES 99 wt % p-iPO EX-33 Dimethylamine 1 wt % p-iBO + 26.1 18.3 14.3 11.9 14.7 YES YES 99 wt % p-iPO EX-34 Didecylamine 1 wt % p-iBO + 18.3 16.4 6.3 5 5 YES YES 99 wt % p-iPO Ex-35 1-hexylamine 1 wt % p-iBO + 22.7 17.5 10.9 9.6 10.4 YES YES 99 wt % p-iPO Ex-36 1-Octadecylarnine 1 wt % p-iBO + 18.6 16.6 6.5 5.2 5.4 YES YES 99 wt % p-iPO Comp. 9 1-pentylamine 1 wt % p-iBO + 24.5 17.9 12.2 11.5 12.6 NO NO 99 wt % p-iPO

TABLE 5 Diesel Compatibility of Polyurethane made with 95% or 99% p-iPO + 1 or 5 wt % piBO and IPDI or MDI with No cap segments (MW = 2000 to 4000) Diesel compatibility (1 wt %) p-iPO p-iPO (NCO/OH Mn = 2000 Mn = 4000 Example molar Polyol EX 37-42; EX 37-42; # ratio) NCO (bis OH) Comp 10-11 Comp 10-11 EX-37 0.1 IPDI 5 wt % p-iBO + YES YES 95 wt % p-iPO EX-38 0.8 IPDI 5 wt % p-iBO + YES YES 95 wt % p-iPO EX-39 0.1 MDI 5 wt % p-iBO + YES YES 95 wt % p-iPO EX-40 0.8 MDI 5 wt % p-iBO + YES YES 95 wt % p-iPO Ex-41 0.1 IPDI 1 wt % p-iBO + YES YES 99 wt % p-iPO Ex-42 0.8 IPDI 1 wt % p-iBO + YES YES 99 wt % p-iPO Comp. 10 0.1 MDI 1 wt % p-iBO + YES YES 99 wt % p-iPO Comp. 11 0.8 MDI 1 wt % p-iBO + YES YES 99 wt % p-iPO 

1. A method for preserving wood; said method comprising contacting wood with a wood treatment composition comprising: (a) a polyurethane polymer synthesized from i) a polyol, and ii) an isocyanate; (b) at least one organic solvent; and (c) at least one wood preservative selected from among halogenated isothiazolinone biocides, halogenated carbamate fungicides and azole fungicides; wherein the polyol comprises from 1 to 5% poly-i-butylene oxide +99 to 95% p-propylene oxide; and
 2. The method of claim 1 in which the wood preservative is 4,5-dichloro-2-n-octyl-4-isothiazolin-3-one.
 3. The method of claim 1 wherein the organic solvent comprises diesel.
 4. The method of claim 1 wherein the isocyanate is isophorone diisocyanate.
 5. The method of claim 1 wherein the isocyanate is polymeric methylene diphenyl diisocyanate.
 6. The method of claim 1 further wherein the polyurethane polymer comprises a capping agent selected from the group consisting of a primary amine having a carbon chain length of ≥C₆, a mono alcohol, and a secondary amine.
 7. A wood treatment composition comprising: (a) a polyurethane polymer synthesized from i) a polyol, ii) an isocyanate; and iii) a capping agent (b) at least one organic solvent; and (c) at least one wood preservative selected from among halogenated isothiazolinone biocides, halogenated carbamate fungicides and azole fungicides; wherein the polyol comprises from 1 to 5% poly-i-butylene oxide +99 to 95% p-propylene oxide; and further wherein the capping agent is selected from the group consisting of a primary amine having a carbon chain length of ≥C₆, a mono alcohol, and a secondary amine.
 8. The wood treatment composition of claim 7 further wherein the polyurethane polymer comprises a capping agent selected from the group consisting of a primary amine having a carbon chain length of ≥C₆, a mono alcohol, and a secondary amine. 